1. Field of the Invention
The present invention relates to a reproducing machine having a document feeding apparatus and an exposure processing portion wherein documents in a document bundle stacked on a document stacker are fed one by one to a document glass plate and, after an exposing process, they are returned to the document stacker, and the steps of feeding and returning of the documents are repeated at every circulation of the documents bundle, so that a single copy of the documents can be obtained at every circulation of the document bundle.
2. Description of the Prior Art
Generally speaking, some reproducing machines of this kind have no sorting apparatus, so that in case the number of documents is large and the copy number is also large, the production capacity or power of the machine is limited. In order to increase the power or production capacity it is necessary to increase the copy speed of the reproducing machine and to enhance the document changing speed of the document feeding apparatus as high as the processing power of the reproducing machine permits.
If the copy speed of the reproducing machine is increased, however, the feeding speed of the copy paper must inevitably be increased. In case that the processing power or production capacity of the reproducing machine is 70 cpm, for example, a processing speed of more than 400 mm/sec is required. In a paper feeding system for feeding copy papers one by one at every single copy cycle in which a document sheet is fed from the document stacker through the exposure processing portion and returned to the document stacker in order to meet the above requirement, the feeding speed of the copy paper becomes 1,000 mm/sec, and damage to the copy paper, an increase of the driving sound and a reduction of reliability can be expected.
Accordingly, in case that the copy speed of the reproducing machine is increased, it is necessary to set the feeding speed of the copy paper similar to said processing speed (400 mm/sec). If the feeding speed is set as above, a plurality of copy papers always remain in the feeding path of copying paper. Accordingly, if the copy of two sheets document is finished by one cycle, for example, it is enough to feed two sheets of copy paper. However, if the document feeding speed (document exchanging speed) of the document feeding apparatus is enhanced to a value as high as the production capacity of the reproducing machine, a copy paper for the document following the said two document sheets is also fed in the paper feeding path of the copy paper and remains in the paper feeding path after the copying operation has been finished, which would make trouble.